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<span id="OMP_005fPROC_005fBIND-_002d_002d-Whether-threads-may-be-moved-between-CPUs"></span><h3 class="section">4.10 <code>OMP_PROC_BIND</code> &ndash; Whether threads may be moved between CPUs</h3>
<span id="index-Environment-Variable-9"></span>
<dl compact="compact">
<dt><em>Description</em>:</dt>
<dd><p>Specifies whether threads may be moved between processors.  If set to
<code>TRUE</code>, OpenMP threads should not be moved; if set to <code>FALSE</code>
they may be moved.  Alternatively, a comma separated list with the
values <code>PRIMARY</code>, <code>MASTER</code>, <code>CLOSE</code> and <code>SPREAD</code> can
be used to specify the thread affinity policy for the corresponding nesting
level.  With <code>PRIMARY</code> and <code>MASTER</code> the worker threads are in the
same place partition as the primary thread.  With <code>CLOSE</code> those are
kept close to the primary thread in contiguous place partitions.  And
with <code>SPREAD</code> a sparse distribution
across the place partitions is used.  Specifying more than one item in the
list will automatically enable nesting by default.
</p>
<p>When undefined, <code>OMP_PROC_BIND</code> defaults to <code>TRUE</code> when
<code>OMP_PLACES</code> or <code>GOMP_CPU_AFFINITY</code> is set and <code>FALSE</code> otherwise.
</p>
</dd>
<dt><em>See also</em>:</dt>
<dd><p><a href="omp_005fget_005fproc_005fbind.html">omp_get_proc_bind</a>, <a href="GOMP_005fCPU_005fAFFINITY.html">GOMP_CPU_AFFINITY</a>,
<a href="OMP_005fNESTED.html">OMP_NESTED</a>, <a href="OMP_005fPLACES.html">OMP_PLACES</a>
</p>
</dd>
<dt><em>Reference</em>:</dt>
<dd><p><a href="https://www.openmp.org">OpenMP specification v4.5</a>, Section 4.4
</p></dd>
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